How do biology and culture interact?

In the year of Darwin, I'm not too surprised at the number of articles being published on the interactions between cultural change and biological evolution -- this synthesis, if achieved, will certainly be a crucial step in explaining how humans evolved. Still, it's unlikely we're going to see the Darwin of culture in 2009, given we're still disputing some of the fundamentals surrounding these two modes of evolution. One of these key arguments is whether or not culture inhibits biological evolution. That we're seeing accelerated changes in the human genome seems to suggest (for some) that culture is one of these evolutionary selection pressures, as John Hawks explains:

Others have sometimes had the view that culture should replace genetic change in recent human history. I think that's wrong. Culture constrains genetic changes. Some kinds of cultural evolution can fall into relatively stable patterns that allow longer-term genetic changes to happen -- like the sustained subsistence changes brought on by agriculture. Those are great targets for adaptive genetic changes, and they might even generate circumstances that enable further cultural changes. That's a true biocultural evolutionary feedback.

Other cultural systems continue to fluctuate more rapidly. But this is nothing new -- many environmental changes fluctuate on a time scale too rapid for genetic changes to catch up. Even so, sometimes genetic polymorphisms occur as equilibrium solutions to such rapidly fluctuating systems. In any event, we can address these questions quantitatively. (Biology and Culture in Recent Selection)

But what about language? Certain aspects of language, particularly arbitrary linguistic constraints, are often seen as a moving target -- too fast for the coevolutionary hypotheses to mould a putative language module. In a recent article over at Babel's Dawn, Edmund Bolles discusses a paper by Morten Christiansen, Florencia Reali and Nick Chater, who argue a language-specific module is implausible, especially one shaped via the Baldwin effect. In the paper, three simulations were run: 1) to establish the Baldwin effect, 2) to show that language change eliminates the Baldwin effect, and lastly, 3) to consider a language-gene coevolutionary scenario. In the latter simulation, the Baldwin effect does work, but only when the genetic influence is high (~50%). Of course, this entails a strong pre-existing genetic basis, leading back to the initial question: what gave rise to the language module? Here's part of their conclusion:

Although our results demonstrate that the Baldwin effect may apply to functional properties of language (Simulation 1), the Baldwin effect is unlikely to be the mechanism for genetic assimilation of arbitrary linguistic properties that began as learned cultural conventions (Simulations 2 and 3). Thus, a highly intricate and abstract language “module”, “instinct”, or “organ” postulated to explain language acquisition, language universals, and the species-specificity of human language could not have arisen through biological adaptation.

[...] this suggests that the biology of language results primarily from exaptation, not adaptation. If this is so, language may have been shaped to a large extent by evolutionary processes of cultural transmission across generations of language learners. These processes include grammaticalization, the continual routinization, generalization, and erosion that underlie historical patterns of language change. Importantly, such cultural evolution is constrained by properties of the human neural and perceptuo-motor systems, which themselves have a genetic basis largely predating the emergence of language. (Chater, Reali and Christiansen, 2009)

Elsewhere, there's an ongoing academic battle between W. Tecumseh Fitch and Derek Bickerton over at the language log. The initial post by Fitch called for a greater recognition of Darwin's theory of language origins: essentially, musical protolanguage provided the initial basis from which the fully fledged symbolic system we all use today, evolved. As Fitch explains in his conclusion:

By placing vocal control at the centre of his model, Darwin availed himself of the rich comparative database of other species who have independently evolved complex vocal imitation, and he thus explains two of the features of human language that set if off most sharply from nonhuman primate communication systems: vocal learning and cultural transmission. The biggest missing piece in Darwin's model, as I see it, is a reasonable explanation of phrasal semantics (and the aspects of syntax that go with it), but this gap was filled by Jespersen by 1922. Together, these hypotheses provide one of the leading models of language evolution available today (for an enthusiastic book-length exploration see Mithen, 2005), and one that has been repeatedly re-discovered by later scholars (e.g., Brown, 2000; Livingstone, 1973; Richman, 1993).

Bickerton wasn't too impressed:

Animal calls — if translated into humanese, and that turns out to be a very dodgy business in itself — are, like holophrases, often the equivalents of whole clauses: "Mate with me"; "Stay off my territory"; "Terrestrial predator coming — get up a tree". Split these into their components and for a few glorious moments it seems that the transition problem has been solved. But in Adam's Tongue I go more deeply into the transition problem than anyone ever has before. And it's the transition problem — how any species could get from a standard animal communication system to even the crudest and most basic kind of protolanguage — that lies at the very heart of language evolution, and without which all "explanations" are mere hand-waving, smoke and mirrors.

Here's the latest rejoinder from Fitch, which I've yet to read. Either way, the debate is a fascinating for anyone interested in language evolution -- and some of the strong characters involved.

For more commentary on the Fitch and Bickerton debate, and more generally for a good site to keep in your RSS feed, go over and visit Shared Symbolic Storage.